Bay Area residents pollute San Francisco Bay every year with enough trash to fill 100,000 kitchen garbage bags, according to the first comprehensive study of the volume of litter flowing into the bay.

The tidal wave of fast-food wrappers, plastic bottles, paper bags and cigarette butts rolls across the landscape and into storm drains, where the garbage washes into creeks and the bay in wet weather. Although it may not be surprising that because of their size San Jose and Oakland pollute the most, tiny Colma in San Mateo County and a host of East Bay cities, including Pittsburg, El Cerrito and Richmond, are among the areas that add the most litter per capita, according to an analysis by this newspaper.

"This is 100 percent preventable. Trash doesn't happen by itself. If we can get people to modify their behavior, we'll make huge gains," said Geoff Brosseau, executive director of the Bay Area Stormwater Management Agencies Association, the Menlo Park group that compiled the report.

The study is part of a massive effort to clean up trash in bay waters. In 2009, state regulators required cities and counties to reduce the amount of trash going into the bay by 40 percent by 2014 or face fines, with a goal of reducing it 100 percent by 2022.

The first step was for cities to estimate current conditions. The study concluded that 1.36 million gallons of trash flow through storm drains from 76 cities and county land in Santa Clara, Alameda, Contra Costa and San Mateo counties each year into creeks and the bay. San Francisco, which has a unique system that collects sewage and stormwater together and filters it all at treatment plants, was not included. Nor were North Bay counties that won't be covered under the new state rules for several more years.

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The study -- completed this month -- used gallons, rather than pounds, to measure volume, because much of the trash, such as plastic wrapping, is very light.

The trash is not only ugly, it also can choke wildlife and tangle boat propellers. Much of it washes into the Pacific Ocean, where it contributes to the Great Pacific Garbage Patch, a vortex of plastic trash north of Hawaii.

To meet the 40 percent reduction by 2014, some places, such as San Jose and Alameda County, have banned plastic bags at supermarkets. Others, such as Oakland, have banned plastic foam packaging at restaurants. Still others have increased street sweeping or installed underground devices to catch trash in storm drains.

"It's a challenge for municipalities," Brosseau said. "There's very little interest in raising taxes. They probably can't afford to put in filters everywhere. It's more effective to go after the sources of the trash."

San Jose ranks first on the litter list, with 168,673 gallons of trash going into creeks and the bay. San Jose officials said there's a logical reason: Their city has the most people and acres of any Bay Area city.

"When you have more property, you have more litter," said Jennifer Garnett, a spokeswoman for San Jose's Environmental Services Department. "It is a pervasive problem across the Bay Area. We all need to do our part."

By 2014, San Jose plans to cut litter flowing into its 1,150 miles of storm drains by 54 percent, Garnett said. The cost: about $6.2 million.

Already, San Jose has passed the most far-reaching bag ban of any Bay Area city, outlawing plastic bags at most markets and retailers, in addition to forcing stores to charge for paper bags. It has banned plastic foam at city events and is considering a ban at restaurants. It plans to put in 118 screens at storm drain inlets in high-trash areas and nine large trash-capture devices in storm drain tunnels. The city also works with the U.S. Environmental Protection Agency to enlist homeless people to clean creeks around homeless encampments.

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Oakland, with 98,625 gallons, is second on the list. The city has put five large trash-capture devices -- think massive strainers that catch debris -- in its 402-mile storm drain system, and it has plans for three more this year. It draped floating booms in Lake Merritt to catch trash from creeks. And it's working to expand volunteer cleanup programs.

"Since we've been working on these things, there's been an absolute, tremendous difference," said Lesley Estes, Oakland's watershed and stormwater management supervisor. "You can see it at Lake Merritt. It's a different place."

Ranked per capita, Oakland and San Jose do well, coming in below the Bay Area average of 260 gallons of trash per 1,000 people. Top on that list is the tiny city of Colma, with 516 gallons.

The estimates were done by fitting 149 storm drains around the Bay Area with trash-capture devices, and analyzing surrounding land uses. Commercial and high-density residential areas -- common in many East Bay cities that rank high on the per capita list -- had the most trash. Parks and rural residential areas had the least. The study then came up with total litter estimates by looking at each city's land uses and factors such as the frequency of street sweeping.

"We have a Best Buy, two Home Depots and an auto row," said Brad Donohue, Colma's acting public works director. "And we have less than 2,000 residents. That skewed the data."

To reach the 40 percent reduction goal, environmentalists say, cities must install trash-catching devices and ban plastic bags and plastic foam containers, rather than just running public education campaigns.

"Some municipalities will resist effective methods that have costs," said David Lewis, executive director of Save the Bay. "That's natural. But these are legal requirements. And the bay has been paying the costs of noncompliance for years."